setInterval 与 clearInterval的使用

onShow: function () {
        var that = this
        that.getOrder()
},
getOrder:function(){
        var that = this
        if (that.data.interval) {
            clearInterval(that.data.interval)
        }
        var interval = setInterval(function () {
            // ... 获取订单
        }, 2000)
        that.setData({
            interval: interval
        })
    },